Movie magic is a delicate thing. You love a movie, it sparks your interest in something which you pursue, you become educated on the topic, and finally you return to the source of the inspiration only to realize the magic is gone. And what fun is it to watch a magic trick when you know how it's done. On the flip side, if you still love a film despite 'knowing better', is that what makes the great ones great? Personally, I say nay. A movie is neither good nor bad in and of itself, only enjoyed or disliked (except Sexy Beast, that movie was crap).
Ideally, I like to go into a movie with as little foreknowledge as possible. In a perfect world unlabeled dvds would be slipped under my door, and somehow they would be the kind of dvd that doesn't give away the whole movie in the menu screen but rather it would just start. The first thing I want to see is the Copyright disclaimer screen, so I know I have 20 seconds to go grab the cup of coffee I left in the kitchen and then the movie begins. [/thinking out loud]
edit: This is the reason I tend to just skim the forums. Also I generally don't much like discussing movies I enjoyed, because.... well, selfish though it may be, I don't want anyone taking a piece of magic out of a movie I like. I have no qualms about having to remain ignorant to enjoy some movies. Bad movies though, I'll tear down what I think needs tearing down.